Apparatus for rotary drilling of wells using casing as the drill pipe

ABSTRACT

A drilling system employing casing as drill pipe and a bit section which is bodily insertable and removable through the casing and releasably attachable thereto for rotation with the casing.

United States Patent Cicero C. Brown 1 c/o Brown Oil Tools, Inc., P.0. Box 19236, Houston, Tex. 77024 Oct. 8, 1969 Jan. 5, 1971 Continuation-impart of application Ser. No. 803,911, Mar. 3, 1969, Continuation-inpart of application Ser. No. 857,046, Sept. 11, 1969.

Inventor Appl. No. Filed Patented APPARATUS FOR ROTARY DRILLING OF WELLS USING CASING AS THE DRILL PIPE 12 Claims, 13 Drawing Figs.

U.S. Cl 175/261, 175/267, 175/284 Int. Cl. .Q F211) 9/26 Primary Examiner-James A. Leppink Attorney-R. Werlin ABSTRACT: A drilling system employing casing as drill pipe and a bit section which is bodily insertable and removable through the casing and releasably attachable thereto for rotation with the casing.

g es! PATENTED JAN 5 :sn

SHEET 2 OF 4 CICERO 6. BROWN A TTORNE Y PATENTEU JAN. 5 |97l SHEET 3 BF 4 CIGERO C. BROWN I N VEN TOR.

A TTORNEY PATENIEUJAM 51971 v sum w 4 C/CERO aBRowN l N VEN'I OR.

A TTO RNEY APPARATUS FOR ROTARY'DRILLING or WELLS usnsc RELATEDYAPPLICATIONS' -This application is a continuation-in-part of my copending applications, Ser. :No. 803,91 1,'filed Mar. 3, 1969; and ser. No.857,046,filedS 'ept-.11,1969.

In the drilling of wells-for oil and gas,- for example by the rotary method, the drilling is convehtionallydone by the em ployment of'relatively smalldiameter string of drill pipe-to CASING AS THE mum. PIPE which a bit is secured, the entire string being rotated to drill the borehole. After'a suitable interval has been drilled, sometimes only a short distance'but at other times for the full depth of the well, casing larger in diameter than the drill pipe will be run into the'jborehole and subsequently cemented to seal off the formations through'whichfthe'borehole extends. This 1 necessarily involves the series of operations in which'the drill string must be extended asthe hole deepens, as by the addition of sections to the drill pipe, and also the entire drill string must be withdrawn whenever it'becomeneces'saryto replace the bit and then reinsert it toresume drilling. Thus making'of such sowith the-drill string outof the well, controlof the well becomes more'difficult. v

Heretofore numerous e, 'rtshavebeen made to provide a system employing the casing itself as the drill pipe in order to overcome some of the hazards enumerated, as well as time anchored to the landing shoe and with the underreamers in theirlextended position;

7 loss; However, thesepriori efforts have not'proven satisfactory l for-various reason well-knowntoithose skilled in the art. Y

The present invention, therefore, is directed to an improved arrangement by which 'theicasing "may'xbe employed as the drilling string andwhen used in combination with aretractable v or removable bit-sectionwillperforni all of the functions of drilling and casing of a well in a sequence-or series of operations which thereby greatly facilitates drilling operations. c

In accordance with 'tlie pr esent inventionja bit section is radially extendible and retractable underreamers, the entire bit section being arranged-and constructed to be insertable bodily through the bore of the 'casingand moved to'the lower end of the casing either on awire line or by simply dropping it into the casing, where, either by gravity alone or supplemented by pumped fluidfpressure, the bit section will be forced t'o'the bottom of the lower'end'of the casing string,

engageable with appropriate latch grooves or other anchorengaging structure in the landing shoe. The latter, in the illustrative embodiments, includes .a number of keys or splines which 'are adapted to engage appropriate spline slots or grooves in the bit section to lock the bit section to the casing against relative rotation whereby rotation of the casing string will be effective to rotate the bit for purposes of drilling the well.

The bit section also includes connector means pivotally connected by crank meansthe the underreamers which will be actuatable from theupper end of the casing string by a suitable running tool by mechanical means or by hydrostatic force, as by drillingfluid circulating through the system, for purpose of extending or actuating the underreamers so as the enlarge the bore hole drilled-by the, pilot bit sufficiently to allow free downward movement of the casing behind the bit as the hole is to the movement of the connector means to the underreamer extending position to direct and confine fluid flow to the bit discharge passages while drilling. This valve arrangement assures high velocity wash fluid and minimizes wash fluid requirements. g

Novel lock means'are provided to lock the underreamers in extended position'contemporaneouslywith the closing of the bypass valve means.

To withdraw the bitsection a conventional fishing tool or -spear is run into the casing on a wire line connected to anchorreleasirig elements of the bit section, whereby an upward pull applied to the fishing tool will be efi'ec'tive to retract the underreamers and release the bit section from the landing shoe to which it has been anchored. The spacing arrangement between the underreamers and anchor elements is so designed as to assure that the underreamers are fully retracted before a the bit section is released, therebyavoiding damage to the unj iderr'eamers which might otherwise occur if they were not completely retractedwhen they pass through the lower end of the'landing shoe. v

Other and more specific object's'and advantages of this invention will become more readily apparent from the following detailed description when read in'conjunction with the accompanying drawing which illustrates a useful embodiment and modification thereof in accordance with the present invention.

'In the drawing: FIG. 1 is a longitudinal, sectional view showing the bit section inserted into the landing shoe preparatory to anchoring the bit section to the landing shoe;

FIG. 2 is a view similar to FIG. 1 showing the bit section FIG. 3 is apartial view generally similar'to FIG. 2 showing the bit section in drilling position with the running tool being withdrawn from the casing;

. "FIG. 4 is a partial longitudinal view similar to FIG. 3 with the' parts in drilling position and the running tool completely withdrawn; v FlG. 5 is a viewsimilar to FIG. 4 showing a retrieving tool inserted in the bit section preparatory to withdrawing the v I latter from the landing shoe; providedwhich includes both the primary bityand a plurality of FIG.6 is a view similar to FIG. 5 showing the parts in released position for withdrawal by the retrieving tool;

b FIG. 7 isa' partial longitudinal view generally similar to the preceding views showing a modifications of the underreamer latch structure;

' FIG. 8 is a longitudinal view of the drilling system in a well bore showing the casing string with the bit section in place in the landing shoe and the drive connections at the surface;

' FIGS. 9 and 10 are longitudinal quarter-sectional views showing, respectively,'the runningand drilling positions of a hydraulically-actuated modification of the bit section;

FIGS. 11 and 12 are cross-sectional views taken on lines 11-11 and 12-12 respectively, of FIG.'1; and

FIG. 13 is a cross-sectional view taken along line 13-13 of P16. 2.

Referring to the drawing and considering the first FIG. 8, there is shown a string of casing C carrying the bit section, designated generally by the letter B, showing the bit section in place in a landing shoe 10 connected to the lower end of casing C At its upper end casing C is connected to a power sub P which functions to rotate the casing string during drilling, as will be described. Power sub P is of the general form and construction. disclosed in my copending application, Ser. No. 736,179, filed June 11, 1968 nowU.S. Pat. No. 3,467,202. A suitable drive connection between the power sub and the casing is disclosed in my U.S. Pat. No. 3,467,202. Power sub P is I suspended from a swivel S carried on elevators E conventionally employed as part of the drawworks of a drilling rig. The swivel has a hose connection H by which conventional drilling fluid is pumped into the drill string of casing C, thence through the passages in the bit' section into the annulus defined by the bore hole surrounding the drilling string, the bore hole being designated by the letter W.

Returning now to FIGS. 1 and 2, the landing shoe and bit section B comprise the basic drilling structure which is secured to the casing. Shoe is provided with an internally, threaded socket '12 by which it is threadedly secured to the lower end of casing C. Adjacent its lower end shoe 10 is provided with two or more angularly spaced cylindrical pins 14 which project a short distance inwardly of the bore of the shoe and form male splines for purposes which will be explained shortly.

Bit section B comprises a body 16 having a bore 17, and is dimensioned to be insertable through the bore of casing C and into the bore of shoe 10. Body 16 is provided about an intermediate portion thereof with a plurality of longitudinal keyways or spline grooves 18 adapted to receive the projecting ends of the pins 14, whereby body 16 will be locked to shoe 10 against relative rotation so that rotation of casing C will function to rotate body 16 and its appurtenances. Spline grooves 18 terminate in upper end walls 19 which form stops for engagement with pins 14 to limit downward movement of the bit body through shoe 10. An annular seal ring 20 is disposed about the exterior of body 16 above end wall 19 to seal with the bore wall of shoe 10. At a point above seal 20, body 16 is provided with a plurality of radial windows or openings 22 in which are mounted anchor dogs 24 of a generally conventional form which are adapted when projected outwardly to be received in an annular anchoring groove 26 formed in the bore wall of shoe 10. The anchor dogs are positioned in body 16 so that they will be in registration with groove 26 when body 16 is fully inserted in the shoe with walls 19 abutting pins 14. The upper end of body 16 is screwed into a ring 28 which overhangs the upper end of the body to define a downwardly facing annular shoulder 30 projecting slightly into bore 17.

A setting sleeve 32, having an axial bore 33, is coaxially slidably disposed in bore 17 and is provided a short distance below its upper end with an external upwardly facing annular shoulder 34 adapted to abut shoulder 30 in the running position of the tool. The exterior of setting sleeve 32 is provided with an annular recess 36 at a point below shoulder 34 adapted to register with dogs 24 when shoulder 34 abuts shoulder 30, as seen in FIG. 1, in which position anchor dogs 24 are free to retract from anchor recess 24. The setting sleeve is also provided with a downwardly facing internal shoulder 37 which projects into bore 33 at a point opposite shoulder 34 for purposes to be described subsequently.

At a short distance below recess 36, sleeve 32 is provided with a plurality of radial windows or openings 38 in which are mounted lock dogs 40 which at a certain stage of operation of the tool, as will be described hereinafter, are adapted to be projected into an annular lock recess 42 provided in the wall of bore 17.

A lock sleeve 44 having an axial bore 45 is coaxially slidably disposed in bore 33 of the setting sleeve and is provided a short distance below its upper end with an external upwardly facing annular shoulder 46 adapted to abut shoulder 37 in the running position of the tool. Lock sleeve 44 is provided with an external annular lock recess 48 adjacent its lower end spaced to be in registration with lock dogs 40 when shoulder 46 is engaged with shoulder 37 in the running position so as to allow lock dogs 40 to be in retracted position during running of the tool. Bore 45 of the lock sleeve is provided with an annular recess 45a intermediate its ends which is adapted for engagement by retrieving tool as will appear subsequently.

The lower end of body 16 carries a downwardly facing internally threaded socket 50 adapted to receive the externally threaded shank 51 of a bit 52 which constitutes the primary or pilot bit and may be of any conventional design for drilling a bore hole to any desired nominal diameter determined by the dimensions of the bit. At a point between the lower ends of splines 18 and socket 50, body 16 is provided with a plurality of longitudinally extending radially opening slots 53 in which are mounted underreamers 54 of any suitable and known design mounted to arms 55. The latter are pivotally mounted on pivot pins 56 which extend transversely of the respective slots for enabling the underreamers to be angularly moved as to be radially projected and retracted with respect to the slots 53. A tubular nozzle 57, having a bore 58 is secured to the lower end of lock sleeve 32 and projects downwardly centrally of the tool. The lower end of nozzle 57 defines a sleeve valve 59 having an annular seal ring 60 seated in the bore thereof and arranged to telescopically receive a tubular extension 61 secured to the upper end of socket 50, when nozzle 57 is moved downwardly relative to extension 61, as will be described subsequently. Each of the underreamer arms 55 is fixedly connected to an angularly extending crank arm 62 having its free end secured to a crosshead pin 63 mounted in a crosshead groove 64 formed in the exterior of nozzle 57 at a point above valve 57 (see FIG. 13). With this arrangement it will be seen that the movement of nozzle 57 downwardly will act through crank arms 62 to rotate the underreamers outwardly and upwardly while reverse movement of the nozzle will act to retract the underreamers. The same movement of nozzle 57 will simultaneously function to open the valve means formed by sleeve valve 59 and the upper end of extension 61. The lower end portion 65 of the latter is conically enlarged to form the connection to socket 50 and the sloping walls of portion 65 are provided with a plurality of jet nozzles 66 positioned to direct a spray of high-pressure wash fluid against the underreamer cutters when the latter are in extended position (FIG. 2) to clean the surfaces of the cutters. The lower end of landing shoe 10 is provided with downwardly tapering slots 11 shaped to cooperate with arms 55 to limit the outward movement ofthe underreamers to the extent desired.

The embodiment illustrated in FIGS. 1 to 6, inclusive, is designed to be run on a suitable running tool, designated generally by the letter R, which may, in turn, be run on a conventional sand or wire line string, or on a string of tubing (not shown). As illustrated tool T includes a tubular body 70 having a lower end portion 71 designed to be inserted in an annular space between the upper end portions of setting sleeve 32 and lock sleeve 44 and to seat against a shoulder 72 in the bore of the setting sleeve. A shear pin 73 initially secures portion 71 to the upper end portion of setting sleeve 32. A collar 74 surrounds the exterior of the lower portion of body 70 and the exterior of the upper end portion of setting sleeve 32 and is secured to body 70 at a point above shear pin 73 by means ofa second shear pin 75. In this position the lower end of collar bears against the upper end of body 16 (FIG. 1). The upper end of collar 74 has an inwardly turned lip 76 abuttable by an external shoulder 77 on body 70 at a point slightly above shear pin 75. A tubular plunger 78 is mounted in the bore of body 70 and is biased downwardly against the upper end of lock sleeve 44 by means of a spring 79 held in compression against the upper end of plunger 78 by means of a backup collar 80 mounted in the bore of body 70. Backup collar 80 is provided with radially extending adjustment pins 81 which project through longitudinally extending slots 82 formed in the upper end of body 70 into an annular recess 83 formed in the bore of a threaded coupling 84 which serves to connect the running tool to a running connection 85 which forms a part of the running string. Plunger 78 is provided with an external shoulder 78a with an opposed shoulder 78b in the bore of body 70 for purposes which will be made apparent subsequently.

In operation, the bit section secured to running tool R will be inserted into the upper end of easing C and will be lowered through the bore of the casing until the bit is brought to a stop by the engagement of pins 14 with end walls 19 of spline grooves 18. At this stage, as the bit section is lowered into place, sleeve valve 59 will be separated from the upper end of extension 61, permitting free bypassing of well bore fluids through the bore of bit section which might otherwise hinder the movement of the bit section through the casing. The parts of the bit section will be positioned as illustrated in FIG. 1 in which the setting sleeve is held in its retracted position by shear pins 73 and 75. Anchor dogs 24 will thus be free to retract and are effectively retracted into relief groove 36.

whereby, to allow the free movement of the bit section through the casing and into landing shoe 10. At the same time, lock dogs 40 will be in their retracted position effectively holding lock sleeve 45 in its upper or inactive position, as seen in FIG. 1.

With the bit section thus in place in the landing shoe, upward jarring force is applied through the running string to break shear pin 75. Thereupon springs 79 will drive plunger 78 downwardly and bring shoulders 78a and 78b into engagement so that the downward force will be transmitted to setting sleeve 32, as well as to lock sleeve 44. The resulting downward movement of both sleeves will drive anchor .dogs 24 into anchor groove 26 effectively locking the bit section to the landing shoe and simultaneously drive lock dogs 40 into locking groove 42, thereby effectively; locking the Setting sleeve to bit. body 10, .being held inthis :position by the downward movement of lock sleeve 45 as seen in FIG. 2. 1

The downwardmovement of the setting sleeve will also be transmitted via nozzle 57 through the crosshead pins 63 and crank arms 62.,to underreamer arms 55-to swing the underreamers to their extended positions. I

Runningtool R may, now:be released by jarring upwardly with sufficient force to break shear pins 73 (FIG. 3), whereupon the running tool'may be removed from the well leaving the ,bit" section secured to the landing shoe with the underreamers in extendedoperating position (FIG. 4).

Power sub P may now be connected tothe upper end of the casing and rotation of .the latter as the drill string will be effected to drill the well as indicated in FIG. 8.

The drilling fluid circulation will be through hose connecbore of easing C. Thence, through the bit section, the fluid flowing through the bores of sleeves 44 and 32 to bore 58 and through the now-closed bypass valve to the discharge passages in the pilot bit and the jet nozzles 66. The 'mud flush will return to the surface through the annulus between well bore W and casing C. Y I

When necessary to withdraw the bit section from the casing in order to replace or repair the pilot bit, underreamers or any other part of the bit section, a. fishing tool, designated generally by the letter T, of the form illustrated and described in my copending application," Ser. No. 869,563, filed Oct. 27, 1969, or of any other generally conventional form, the details of which do not form a part of this invention, will be run into the casing bore on a wire line, or tubing string if desired, and will be 'latched'into groove 45a of-loclrsleeve 44, as seen in FIG. 5. On application of upward pull to the fishing string, the lock sleeve will be drawn upwardly bringing shoulders37 and 46 in abutment and placing lock recess 48in registration with lock dogs 40, freeing the latter from recess 42. This same upward movement, now transmitted through abutting shoulders 37 and 46 will raise setting sleeve 32 sufficiently to place recess 36 in registration with anchor dogs 24 which will thus be free to retract from anchor groove 26. Additionally, the upward movement ofthe setting sleeve will be transmitted to nozzle 57 which will, in turn, raise sleeve valve 59 off of the end of extension 62 opening the bypass valve to allow fluid to dump back into the well as the bit section is raised. Further the upward movement of nozzle 57 will rotate the underreamers back to their retracted position inside slots 53. The parts will now be in the same positions as when running into the casing (FIG. 6) and theentire bit section may now be withdrawn through the casing.

iii. drilling is to be resumed, the bit section, with the parts in the original retracted positions, will be returned through the bore of the casing to its lodgment in shoe 10, the bit section anchored and the underreamers extended as described, and drilling will be resumed. a

Fig. 7, illustrates a modification in which the setting sleeve and lock sleeve are effectively combined. In this modification body 16 is provided with an external annular recess 90 at a point spaced between shoulder 30 and recess 36. Setting sleeve 32 is provided with a plurality of angularly spaced previouslydescribed embodiment, will close valve 5961 and I .tion I-l, swivel S and through a conduit in power sub P into the openings or windows 138 (one shown) in which are mounted pivoted latches 140 which are biased by means of springs 91 to urge the upper ends of the latches to swing outwardly of windows 138. With this arrangement it will be seen that when setting sleeve 32 moves downwardly relative to body 16 sufficient to bring the upper end positions of the latches opposite recess 90, the spring pressure on the lower ends of the latches will swing the upper ends of the latches outwardly of windows 138 into recesses 'causing them to abut the shoulder 128 forming the upper wall of recess 90 and thereby locking the setting sleeve in the position at which anchor dogs 24 will be anchored in recess 26. This downward movement, as in the hold the underreamers in their extended positions.

. Running tool R will be slightly modified, as shown, but in general will operate in substantially the same way as the earlier described tool. Similarly, the retrieving tool will be modified so as to swing latches out of recess 90 when effecting release of the bit body from the landing shoe. These modificatons will be readily apparent to those skilled in the relevant art.

FIGS. 9 and 10 illustrate a further modification in which the use of a running tool is dispensed with and the bit section run and set by a combination of gravity and hydrostatic pressure. As-seen in these FIGS., the only structural changes are the provision at the lower end of lock sleeve 44 of a bottom closure plate 92 having a central orifice 93 of relatively restricted dimensions. Also body 16 is provided with an extension 16a which is secured directly to a setting sleeve extension 32a by means of a shear pin 73a to hold the parts in the relatively retracted positions.

In operation, the bit section will be inserted into the casing and allowed to fall of its own weight to lodgment on male splines 14. Pumped fluid may be employed to assist the bit section to move through the casing to its seat. As soon as the bit section is in place on pins 14, pump pressure will be increased and pressure will build up inside lock sleeve 44 by reason of the restricted orifice 93, the various seals including seal 20 preventing leakage of the pressure about the outside of the bit section. When the hydrostatic pressure has built up sufficient force to break shear pins 73a, both sleeves 32 and 44 will be caused to moved downwardly to position driving anchor dogs 24 into anchor recess 26 and lock dogs 40 into lock recess 42. Also, sleeve valves 59'-6l will be closed and the underreamers extended to their operative position where rotation of the casing from the surface will permit drilling ahead.

To remove the bit section when required, a retrieving tool such as that previously described may be run and operated to raise lock sleeve 44 and then setting sleeve 32, with opening of the bypass valve and retraction of the underreamers.

From the foregoing it will be evident that a drilling system is provided in which the casing itself which is ordinarily required to line the bore hole will be used as the drilling string and will be continuously fed into the hole as the drilling proceeds, thereby obviating all of the additional operations conventionally required in rotary drilling and for casing the well. The hazards accompanying the conventional drilling and casing operations, including those arising from round trips" of the drill string, will be obviated, drilling operations greatly facilitated, and time of operation substantially reduced.

Landing shoe 10 may be employed to land conventional tools required for cementing the casing or performing other operations commonly required in completing the well.

It will be understood that various changes and modifications may be made in the details of the illustrative embodiment within the scope of the appended claims but without departing from the spirit of this invention.

I claim:

1.-Apparatus for rotary drilling of wells using casing as the drill pipe, comprising in combination with a string of casing and means for rotating the same:

a. a bit section bodily insertable and removable through the bore of the casing;

b. cooperating means on the bit section and the lower end portion of the casing for landing the bit section therein in nonrotative relation to the casing;

c. said bit section comprising:

i. a generally tubular body;

ii. radially movable anchor means mounted on the body for releasably anchoring the body to said casing portion;

iii. a main bit carried by the lower end of the body having an upwardly extending tubular shank defining a fluid passage through the bit;

iv. a plurality of angularly space underreamers mounted on the body above said bit for radial movement between extended and retracted positions relative to said body;

v. a sleeve member coaxially disposed in said body cooperable with said anchor means and reciprocable between upper and lower positions respectively releasing and actuating said anchor means;

vi. connector means pivotally connecting said sleeve member to said underreamers reciprocable with said sleeve member between said positions for simultaneously respectively retracting and extending said underreamers;

vii. valve means carried by the sleeve member cooperable with said shank for opening and closing communication between the interior of said sleeve member and said fluid passage respectively at said upper and lower positions of said sleeve member; and

vii. releasable means initially securing said sleeve member to said body in said upper position.

2. ln apparatus according to claim 1, wherein said bit section includes lock means carried by said sleeve member operable in response to movement of said sleeve member to said lower position to lock said sleeve member to said body in said lower position.

3. Apparatus according to claim 1 wherein said valve means comprises a tubular nozzle defining a sleeve valve disposed to telescopically receive the upper end portion of said shank.

4. Apparatus according to claim 1 including means responsive to mechanically applied force for releasing said releasable means.

'5. Apparatus according to claim 1 including means responsive to hydrostatic force for releasing and said releasable means.

6. Apparatus according to claim 2 wherein said lock means includes:

a. radially movable lock elements mounted on said sleeve member for releasably anchoring the same to said body; b. a lock sleeve coaxially disposed in the bore of said sleeve member cooperable with said lock elements and reciprocable between upper and lower positions respectively releasing and actuating said lock elements; and c. means actuable in response to the release of said releasable means to simultaneously move said lock sleeve to said lower release position. 7. Apparatus according to claim 1 wherein said cooperating means includes:

a. a tubular landing shoe secured to the lower end of the casing string; b. inwardly projecting male splines in the bore of said shoe;

and c. spline grooves in the bit body open at their lower ends for receiving the male spline in response to relative downward movement of the bit body. 8. Apparatus according to claim 7 wherein said anchor means includes:

a. a plurality of angularly spaced anchor dogs disposed in openings in the wall of said body; and b. an annular anchor groove in the wall of said landing shoe arranged for anchoring engagement with said dogs. 9. Apparatus according to claim 2 wherein said lock means includes:

a. a plurality of angularly spaced latching dogs disposed in openings in the wall ofsaid sleeve member; and b. an annular latching groove in the interior. wall of said body arranged for latching engagement with said latching dogs. 10. Apparatus according to claim 3 wherein said connector means includes:

a. a crank arm angularly secured to each underreamer; and b. a crosshead pin-and-slot connection between the free end of each crank arm and said nozzle. 11. Apparatus according to claim 6 wherein said lock sleeve includes:

a. a closure plate across the bore thereof; and b. an orifice of restricted area through said closure plate. 12. Apparatus according to claim 1 wherein said shank has mounted through the walls thereof a plurality ofjet nozzles arranged to direct wash fluid toward said underreamers. 

1. Apparatus for rotary drilling of wells using casing as the drill pipe, comprising in combination with a string of casing and means for rotating the same: a. a bit section bodily insertable and removable through the bore of the casing; b. cooperating means on the bit section and the lower end portion of the casing for landing the bit section therein in nonrotative relation to the casing; c. said bit section comprising: i. a generally tubular body; ii. radially movable anchor means mounted on the body for releasably anchoring the body to said casing portion; iii. a main bit carried by the lower end of the body having an upwardly extending tubular shank defining a fluid passage through the bit; iv. a plurality of angularly space underreamers mounted on the body above said bit for radial movement between extended and retracted positions relative to said body; v. a sleeve member coaxially disposed in said body cooperable with said anchor means and reciprocable between upper and lower positions respectively releasing and actuating said anchor means; vi. connector means pivotally connecting said sleeve member to said underreamers reciprocable with said sleeve member between said positions for simultaneously respectively retracting and extending said underreamers; vii. valve means carried by the sleeve member cooperable with said shank for opening and closing communication between the interior of said sleeve member and said fluid passage respectively at said upper and lower positions of said sleeve member; and vii. releasable means initially securing said sleeve member to said body in said upper position.
 2. In apparatus according to claim 1, wherein said bit section includes lock means carried by said sleeve member operable in response to movement of said sleevE member to said lower position to lock said sleeve member to said body in said lower position.
 3. Apparatus according to claim 1 wherein said valve means comprises a tubular nozzle defining a sleeve valve disposed to telescopically receive the upper end portion of said shank.
 4. Apparatus according to claim 1 including means responsive to mechanically applied force for releasing said releasable means.
 5. Apparatus according to claim 1 including means responsive to hydrostatic force for releasing and said releasable means.
 6. Apparatus according to claim 2 wherein said lock means includes: a. radially movable lock elements mounted on said sleeve member for releasably anchoring the same to said body; b. a lock sleeve coaxially disposed in the bore of said sleeve member cooperable with said lock elements and reciprocable between upper and lower positions respectively releasing and actuating said lock elements; and c. means actuable in response to the release of said releasable means to simultaneously move said lock sleeve to said lower release position.
 7. Apparatus according to claim 1 wherein said cooperating means includes: a. a tubular landing shoe secured to the lower end of the casing string; b. inwardly projecting male splines in the bore of said shoe; and c. spline grooves in the bit body open at their lower ends for receiving the male spline in response to relative downward movement of the bit body.
 8. Apparatus according to claim 7 wherein said anchor means includes: a. a plurality of angularly spaced anchor dogs disposed in openings in the wall of said body; and b. an annular anchor groove in the wall of said landing shoe arranged for anchoring engagement with said dogs.
 9. Apparatus according to claim 2 wherein said lock means includes: a. a plurality of angularly spaced latching dogs disposed in openings in the wall of said sleeve member; and b. an annular latching groove in the interior wall of said body arranged for latching engagement with said latching dogs.
 10. Apparatus according to claim 3 wherein said connector means includes: a. a crank arm angularly secured to each underreamer; and b. a crosshead pin-and-slot connection between the free end of each crank arm and said nozzle.
 11. Apparatus according to claim 6 wherein said lock sleeve includes: a. a closure plate across the bore thereof; and b. an orifice of restricted area through said closure plate.
 12. Apparatus according to claim 1 wherein said shank has mounted through the walls thereof a plurality of jet nozzles arranged to direct wash fluid toward said underreamers. 